[llvm-commits] [LLVMbugs] [Bug 7322] ms vcpp build warnings

[Chris Lattner]

On Jun 15, 2010, at 12:45 PM, nate begeman wrote:

> Sure, sorry, I seemed to recall shifts implicitly promoting to int, but maybe that's in C and not C++, will cast.

They do promote to int, it just causes warnings with some compilers.

-Chris

> 
> Nate
> 
> On Jun 15, 2010, at 12:05 PM, Chris Lattner wrote:
> 
>> Nate, can you change these to use "nElts << (int)quad" or something?
>> 
>> -Chris
>> 
>> On Jun 15, 2010, at 7:43 AM, Dimitry Andric wrote:
>> 
>>> On 2010-06-14 22:39, bugzilla-daemon at llvm.org wrote:
>>>> --- Comment #1 from Chris Lattner <clattner at apple.com> 2010-06-14 15:39:27 CDT ---
>>>> there are a bunch of build warnings with MSVC.  If you're interested in helping
>>>> with this, please send patches to llvm-commits, thanks!
>>> 
>>> What I see quite often with VC++ is this warning:
>>> 
>>> .\NeonEmitter.cpp(529) : warning C4804: '<<' : unsafe use of type 'bool' in operation
>>> 
>>> which comes from bool variables used as shift count, e.g:
>>> 
>>> bool dummy, quad = false;
>>> ...
>>>  b = Duplicate(nElts << quad, typestr, "b");
>>> 
>>> I'm not sure if this is unnecessarily paranoid of VC++, as the standard
>>> seems to imply it should be no problem, if I read it correctly:
>>> 
>>> [conv.prom]
>>> 4. An rvalue of type bool can be converted to an rvalue of type int,
>>> with false becoming zero and true becoming one.
>>> 
>>> and [conv.integral]:
>>> 
>>> 4. If the destination type is bool, see 4.12. If the source type is
>>> bool, the value false is converted to zero and the value true is
>>> converted to one.
>>> 
>>> In short, is it worthwhile to appease VC++ here, by using an int or
>>> unsigned instead, or should we just stash in a pragma to disable this
>>> particular warning?
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>> 
>